Bookshelf speakers and complex/orchestra

I'd have to believe your Sonus Faber Concertinos can do a very nice job with orchestral music if set up properly.

First , of course, make sure both speakers are hooked up properly and in phase (+ to +, - to -).

Then definitely work on speaker placement first if currently on bookshelves.

Early reflections will jumble busy musical passages such as those often found in large scale orchestral arrangements on even the best systems, so if applicable, try placing the speakers at least a couple of feet out from the walls to give everything some roomk to breath.

Moving speakers further apart might also help by providing a wider sound stage within which the large number of individual instruments comprising orchestral music can be distinguished better.

Bass/low end extension with smaller speakers away from walls could suffer as a side effect of optimal placement otherwise. If so, adding a good, well matched sub is a straightforward way to address the problem.

If none of this helps, then it might be time to look at amplification used and other electronics.

Also, are you using decent interconnects?

While I agree with everyone, I would like to second, or third, the value of speaker placement. Get those speakers out (on stands, of course) from the rear wall three times their depth, minimum, and spread em apart as far as you can without exceeding the distance to your listening position while keeping them two times their width out from your side walls. And, put your listening chair at the apex of an imaginary triangle with your speakers (imaginary, hell, measure it, measure everything). A little longer may be preferred at the end of the day, but shouldn't be by much.

And after you've had this much fun, trying toeing your speakers out 10 degrees or so from head on to your listening position. Last, but not least, clear the wall behind your speakers and side walls of any bulky furnishings. I imagine that they're might be some dissagreement on this, but do try it for yourself.

Yes, full orchestral is the real test for a speaker (solo piano too). Most box speakers get bogged down under the pressure. Dipoles handle it better than most, such as, panel, electrostatic, or the rare open baffle dynamic speakers, by eliminating cabinet resonances. As Shadorne mentioned, dynamic range and transients are critical too. Larger speakers usually handle this better, but that also depends on the quality of the drivers and other factors such as the Qts. Very few speakers do it well.

Another factor is how the speaker interfaces with the room. Poor off-axis response causes a dull reverberant field. The very nonlinear reflected sound throws the whole 'picture' off.